Method for treating beryllium and its alloys



1936. c. H. MONROE ET AL 2,051,963

METHOD FOR TREATING BERYLLIUM AND ITS ALLOYS Filed May 28, 1932 Patented Aug. 25, 1936 UNITED STATES PATENT OFFICE METHOD FOR TREATING BERYLLIUM AND ITS ALLOYS Application May 28, 1932, Serial No. 614,140

11 Claims.

This invention relates to a method for treating beryllium and its alloys so as to enable ready and eife tive' fusion of such metals to secure, among other things, improved structure, increased strength, less brittleness, and more ready machinability. 7

The high melting point of beryllium and alloys with considerable quantities of this metal, the ready oxidation of such metals, and the extreme sluggishness even after fushion, have all conspired against efiicient melting. In the past, it has been customary to fuse beryllium, particularly when present as small particles or flakes (obtained in this manner by fluoride or chloride electrolysis) by pressing the metal into briquettes of convenient size and contacting with a fused flux heated to above 1300 C., the melting point of beryllium being 1285 C. Fluxes used for this purpose have varied, but of necessity they have been limited to halides. Further, the high temperatures reached have made it seem desirable that the major portion of such flux consist of an alkaline earth compound, since the alkali metal halides tend to vaporize rapidly at 1300" C. i Prominent among flux bases has been barium chloride. A good flux for such use is one containing about 90% of this material with about 10% of barium fluoride.

Despite the fact that fluxes containing barium l and other alkaline earth halides as a base give quite effective metal fusions, we have found that they result in the addition to beryllium of a constituent which,'for many purposes, is extremely undesirable. Metal that has been fused in contact with an alkaline earth compound, for example with the barium chloride and fluoride mixtures above described, shows metallographically a constituent which indicates itself as insoluble in the crystal matrix on solidification of the metal 9 and therefore segregates to the boundary of the crystal, forming a lattice-work throughout the mass. This structure is shown in the figure-a drawing of a photomicrograph of beryllium fused in contact with a flux of this type. The latticework of the foreign constituent (it may be a barium compound with beryllium, or some other complex metallurgical constituent insoluble in the major metal) makes for great weakness and brittleness, since each crystal boundary is a source of weakness; once started, failure along a crystal boundary continues without structural opposition.

This same characteristic of boundary constitwent formation applies, not only to beryllium, but equally to the alloys of beryllium containing the metal in preponderance by volume. For example, the alloy containing 70% beryllium and 30% aluminum, by weight, an alloy of particular value in technology because of its great strength and light weight, shows the boundary line constituent 5 in question just as does beryllium itself. This constituent, being very hard, makes extremely diflicult the machining of castings made of.this alloy.

We have found that if alkaline earth compounds (calcium, strontium and barium) are removed from all flux contacting with beryllium and its alloys, this hard and otherwise objectionable constituent is avoided. In the case of pure beryllium, to accomplish this, we have found effective and efficient results resulting from the use of a double fluoride of beryllium and an alkaline metal, such as, for example, Na2BeF4. Metal fused in contact with this compound does not show significant quantities of the troublesome constituent. There is a relative freedom from inter-crystalline constituents when the metal is so melted. There is, of course, some volatilization of the flux by this procedure, but losses so incurred are negligible in importance as compared with the gain in metal structure and metal strength.

Where an alloy of beryllium with another metal is to be made, it is possible to use, instead of an alkali beryllium fluoride, a double fluoride of an alkaline metal and the metal to be alloyed with the beryllium. A mixture of alkali fluoride and the other metal fluoride is, of course, equally satisfactory. For example, where it is desired to make an alloy containing beryllium and aluminum, such 35 alloy is readily obtained by fusing beryllium in contact with molten cryolite, or a mixture of sodium fluoride and aluminum fluoride. Reduction of some or all of the aluminum fluoride to aluminum metal occurs, with immediate alloying action, to form the desired alloy. Similar procedures are availabe for alloys of other metals in the same manner.

We claim:-

1. The process for fusing metallic beryllium and alloys thereof containing at least 50% of beryllium by volume, which process includes contacting the metal with a fluid mass containing an alkali metal halide and a beryllium halide, the contact being eflected while the metal is at fusion temperature.

2. The process for fusing metallic beryllium and alloys thereof containing at least 50% of beryllium by volume, which process includes contacting the metal with a fluid mass containing an alkali metal fluoride and a beryllium fluoride, the contact being effected while the metal is at fusion temperature.

3. The process for fusing metallic beryllium and alloys thereof containing at least of beryllium by volume, which process includes contacting the metal with a fluid mass containing a sodium halide and a beryllium halide, the contact being eifected while the metal is at fusion temperature.

4. The process for fusing metallic beryllium and alloys thereof containing at least 50% of beryllium by volume, which process includes contacting the metal with a fluid mass containing a sodium fluoride and a beryllium fluoride, the contact being eifected while the metal is at'fusion temperature.

5. The process for fusing an alloy of beryllium and aluminum, which process includes contacting the metal with a fluid mass containing cryolite, the contact being effected while the metal is at fusion temperature.

6. The process for fusing an alloy of beryllium and aluminum, which process includes contacting the metal with a fluid mass containing an alkali metal fluoride and aluminum fluoride, the contact being effected while the metal is at fusion temperature.

'7. The process for fusing metallic beryllium and alloys thereof containing at least 50% beryllium by volume, which process includes contacting the metal with a fluid mass containing an alkali metal halide and a halide of a metal being fused, the

contact being effected whfle the metal is at fusion temperature.

8. The process for fusing metallic beryllium and alloys thereof containing at least 50% beryllium by volumefwhich process includes contacting the metal with a fluid mass containing an alkali metal fluoride and a fluoride of a metal being fused, the contact being effected while the metal is at fusion temperature.

9. The process for fusing metallic beryllium and alloys thereof containing at least 50% beryllium by volume, which process includes contacting the metal with a fluid mass containing sodium fluoride and a fluoride of a metal being fused, the contact being effected while the metal is at fusion temperature.

10. The process for fusing metallic beryllium and alloys thereof containing at least 50% beryllium by volume, which process includes contacting the metal with a fluid mass containing an alkali metal halide and an aluminum halide, the

contact being effected while the metal is at fusion temperature.

11. The process for fusing metallic beryllium and alloys thereof containing at least 50% beryllium by volume, which process includes contacting the metal with a fluid mass containing sodium fluoride and aluminum fluoride, the contact being effected while the metal is at fusion temperature. 30

CHARLES H. MONROE. HARRY C. CLAFLIN. 

